In fluid headers (sometimes known as collecting boxes) of this type, fastening together the two profiled elements of the header, and sealing between their marginal regions, are usually ensured by brazing. For this purpose, after the components of the heat exchanger have been fully assembled together, a brazing material is melted. This material is present as a coating on the profiled elements and on the other components of the heat exchanger. This gives, in particular, all at the same time, the required sealed connection between the fluid flow tubes and the corresponding profiled elements, together with that between the terminal walls and the tubular wall of the header.
During handling operations prior to the brazing operations, it is necessary that the two profiled elements keep the relative positions which they have got to have in the complete header. European patent specification number EP 375 896 A describes a fluid header in which the marginal regions of one of the profiled elements are parallel to each other and are either inserted in rebates formed in the marginal regions of the other element, or are in flat overlying relationship with these last mentioned marginal regions. In order to immobilize the two elements with respect to each other before the brazing operation, their marginal regions are "riveted" by means of local deformations, with projections thus formed by one of the elements engaging, as required, in apertures formed in the other element.